Дисертації з теми "Plasmas froids – Modèles mathématiques"
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Layeillon, Lise. "Analyse et modélisation du fonctionnement d'un réacteur de dépôt de silicum amorphe hydrogéné assisté par plasma." Toulouse, INPT, 1992. http://www.theses.fr/1992INPT042G.
Guiberteau, Emmanuel. "Modélisation d'une décharge DC pulsée dans l'azote : simulations numériques à l'aide d'un code couplant la dynamique des particules chargées à celle du gaz neutre : comparaisons avec l'expérience." Nancy 1, 1998. http://docnum.univ-lorraine.fr/public/SCD_T_1998_0291_GUIBERTEAU.pdf.
This work deals the modeling of a dc pulsed diode type discharge used for iron and steel nitriding. The present research aimed at a better understanding of the processes occuring in such plasmas in order to attain an optimization of the surface treatment process. In a first stage we adapted an existing electrical modeling to the experimental results obtained from electrostatic probe and emission spectroscopy measurements. These preliminary results showed a roughly good agreement between the modeling and the experiment and pointed out the limits of this simulation. Two improvements have thus been made to this basic model: a better description of the electron population using a monoenergetic electron beam ; a coupling with a modeling of the neutral gas dynamics. The first improvement led to a better description of the various regions of the discharge (in particular the negative glow) and to get an excellent agreement between numerical and experimental results in the case of short duration impulse discharges. The second improvement showed the importance and the need for taking into account the heating of neutral gas in the case of discharge on-time greater than a few hundreds of microseconds
Dubus, Nicolas. "Contribution à l'étude thermique d'un réacteur à décharge à barrière diélectrique." Poitiers, 2009. http://theses.univ-poitiers.fr/theses/2009/Dubus-Nicolas/2009-Dubus-Nicolas-These.pdf.
This thesis aims to study the thermal behaviour of a laboratory Dielectric Barrier Discharge (DBD) reactor. An experimental study was first realized to measure temperatures at different points of the reactor by using optic fibres. These measurements were performed in transient and steady states. To examine the influence of heat losses , not insulated and insulated reactors were considered. The influence of the nature and the form of the applied voltage was else considered. Experiments were conducted with a sinusoidal voltage and a pulsed power supply
Gaychet, Sylvain. "Modélisation des décharges couronnes négatives : Application à la précipitation électrostatique." Pau, 2010. http://www.theses.fr/2010PAUU3038.
Electrostatic precipitation presents many advantages from the nuclear wastes treatment's point of view. Indeed, this kind of process can capture submicronic particles without producing secondary wastes (no filter media) and without pressure looses in the exhaust circuit. The work presented in this thesis concerns the study of negative corona discharges in air at atmospheric pressure occurring in an electrostatic precipitator (ESP) developed by the CEA (Atomic Energy Committee). The aim of this study is to determine how the electrostatic precipitation dedicated phenomena, especially the specific high voltage generator, the gas temperature and the fact that particles are flowing through the gap then collapsing on the electrodes, modify the discharge to improve the efficiency of ESPs. This work is based on a fundamental experimental study of the negative corona discharge and on numerical simulations of this discharge under conditions close to those of the lab scale ESP developed by the CEA
Zaafrani, Ibtissem. "Dynamique et stabilisation d’un plasma magnétique froid." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0312.
In this thesis, we consider a linearized Euler-Maxwell model for the propagation and absorption of electromagnetic waves in a magnetized plasma. Two types of boundary conditions are considered: perfectly conducting on the whole boundary and Silver-Müller, homogeneous or not, on part of it. First, I establish the equations of the model and show its well-posedness by the theory of semigroups. Then, I am interested in the stabilization of the model. First, I carry out a study on the long- term asymptotic behavior of the solution. I show that it decreases towards zero under certain physically reasonable assumptions. I conclude that it converges to a non-zero stationary state in a larger energy space. This stationary state is linked to the topology properties of the domain, and is expressed as a function of the initial data. Secondly, I study the energy decay rate by using the frequency domain method. I establish a polynomial decay for both boundary conditions. I also prove a conditional exponential decay result in the homogeneous Silver-Müller case. In the perfectly conducting case, we show that the Euler-Maxwell system is not exponentially stable. We conclude by a result of convergence towards the time-harmonic regime in the presence of a harmonic forcing. Among the main difficulties encountered, the resolvent of the evolution operator is not compact and the internal absorption acts only on the fluid variables. No homogeneity assumption is made, and the topological and geometrical assumptions on the domain are minimal. These results appear strongly linked to the spectral properties of various matrices describing the anisotropy and other plasma properties. Finally, we extend those results to the case of a vacuum-plasma interface problem
Quinio, Géraldine. "Modélisation numérique de la génération d’un plasma d’air dans un écoulement aérodynamique." Toulouse, INSA, 2005. http://eprint.insa-toulouse.fr/archive/00000445/.
Order to reduce the flash points in air intake of aircraft, a considered deviee consists in the partial ionisation of the air around the air intake. The aim of the thesis is to develop mathematical and numerical models in order to apprehend the main physical mechanisms which occur in the generation of air plasmas at atmospheric pressure in air flows. An asymptotic analysis of simple ionization kinetics of air flows at atmospheric pressure is first proposed. The existence of the plasma depends on the value of the flow velocity relative to a threshold value and on the existence of metastables which detach electrons from negative ions. Secondly, we were interested in the modelling of capillary discharges which allows the genera tion of a homogeneo us discharge in air at atmospheric pressure. A OD model has been made in order to understand the main physical mechanisms occurring in the discharge initiation. The numerical simulations shows the wall phenomena take an important place in the operation of the discharge. Lastly, a 2D model is developed to model a negative tip/plane corona discharge in air flows. The mode! consists of a system of non-linear convection/diffusion /reaction equations coupled with the Poisson equation. The current induced by the plasma circulation in the extemal circuit is Iinked with the potential through an ordinary differential equation in time. The numerical simulations show that when the flow velocity becomes important, a periodical formation of plasma channels carrying away by the air flow is observed
Irimiciuc, Stefan-Andrei. "Experimental and theoretical studies on the dynamics of transient plasma plumes generated by laser ablation in various temporal regimes." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10193/document.
Laser ablation methods exhibit a fast development in various application fields, as materials processing, medicine, nuclear fusion or analytical sciences. Despite important advances in the knowledge of the complex laser-matter interactions involved in this process, there is still need for better fundamental understanding and modeling. The aim of this work was to experimentally and theoretically investigate the dynamics of transient plasmas generated by laser ablation in various regimes (ns, ps, fs), and to try to correlate the observed behavior with the physical properties of the ablated materials We implemented space- and time-resolved optical, spectroscopic and electrical methods for the study of single-component metallic targets and of complex chalcogenide targets. This led to a space-time mapping of the main plasma parameters. The study performed in actual Pulsed Laser Deposition (PLD) conditions revealed some peculiar effects like ionic oscillations or plume reflection at the substrate. A compact fractal hydrodynamic model was developed to simulate the laser-produced plasma dynamics. The theoretical model accurately describes the spatial and temporal evolution of the main plasma parameters (electronic temperature, expansion velocities, particle number density, Debye length, plasma potential). We report for the first time empirical relations connecting these plasma parameters with the physical properties (electrical/thermal conductivity, atomic mass, heat of vaporization) of the target. These relationships transcend all three ablation regimes (ns, ps, fs)
Annušová, Adriana. "Étude de la cinétique des décharges et post-décharges excitées à hautes et très hautes fréquences dans les mélanges azotés." Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10089/document.
This work focuses on the study of the kinetics of discharges and post-discharges in flowing nitrogen and nitrogen mixtures at moderate pressures. The kinetic modeling was performed on the basis of experimental results in order to understand the production and destruction processes of the species presents in the plasma. The thesis is divided into two parts according to the type of the discharge and gas mixtures studied. In the frame of the part A, a N2-Ar discharge generated by an original helical cavity excited at 27 MHz is examined by optical emission spectroscopy. Based on experimental results, a global kinetic model coupled with a model of the vibrational distribution function of the N2(C3Pu, v’=0-4) state have been developed. These models enable the analysis of our results and demonstrate the importance of the mechanisms involving metastable nitrogen and argon species, i.e. N2(A3Su+) et Ar(3P0,2). In Part B, discharges in mixtures of N2-O2 generated by a 433 MHz coaxial cavity were studied along with the afterglows by optical emission spectroscopy and mass spectrometry methods. A 0D kinetic model, based on experimental results, is associated with a flow simulation in order to qualitatively reproduce the evolution of concentrations and predict the nature of the environment created by the discharge as well as its characteristics for the applications of thin layer deposits of organosilicon materials for microtechnology
Abd, Jelil Radhia. "Modélisation de la relation entre les paramètres du procédé plasma et les caractéristiques de la qualité du matériau textile par apprentissage de données physiques." Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10017/document.
Atmospheric plasma treatment seems to be a good way to treat quickly, cheaply and ecologically textile material surfaces. Despite these advantages, it is extremely difficult to understand the complex non-linear relationship between the plasma processing parameters and the final properties of materials. Therefore, the study and optimization of such process must be based on an exploitation of intelligent techniques such as fuzzy logic and neural networks. In a first part, the impact of atmospheric air Dielectric Barrier Discharge (DBD) plasma treatment is studied on different types of polyester and viscose woven fabrics. In order to get a better understanding on how the structure of woven fabrics influence on the results of the plasma treatment, a selection of the most relevant parameters was carried out by using a fuzzy logic based sensitivity variation criterion. This work shows that that the electric power, the treatment speed, the composition, the fibers fineness, the air permeability, the weave construction and the summit density have an influence on the wettability and the capillarity of fabrics. Lastly, a neural network approach was developed to predict the relationship between the selected input parameters and the fabric hydrophilic properties. Very satisfactory results were obtained and show a good capacity of generalization. Moreover, a quantitative analysis based on the weights of connections was conducted to analyze the relative importance of the input parameters. The results of this analysis are coherent with those obtained by using the fuzzy logic based sensitivity variation criterion. Thus, this finding confirms, on the one hand, the influence of the selected parameters and, on the other hand, it shows the efficiency of neural networks
Daadaa, Rihab. "Formulation mixte augmentée d’un modèle « Full-wave » tridimensionnel dans un plasma froid : analyse numérique d’une approximation ℙ₂-ℙ₁". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0307.
The object of this thesis is to study a numerical simulation method of a so-called “Full-wave” model of the propagation in a tokamak of an electromagnetic wave injected by a set of antennas installed in the boundary of the containment chamber. A Lagrange finite element approximation method is deployed. In the first chapter, we introduced the physical model considered to describe the propagation of an electrostatic wave of a frequency close to hybrid resonance in a so-called cold plasma, plasma confined by a magnetic field inside a tokamak. The propagation of electromagnetic waves is modeled by Maxwell's equations. This work contemplates an approximation of the time-harmonic solution. In the second chapter, we recall the mixed and mixed variational formulations already studied in the past. These formulations allow us to find solutions in (H¹(Ω))³ and therefore a conformal finite element approximation in this space. Chapter three is dedicated to the presentation of the discretization of the model's equations in three dimensions of space. In chapter four it is demonstrated the well-posed character of the discrete system of equations when one considers a Taylor-Hood type approximation ℙ₂-ℙ₁. In this section, we proved a result about the existence and the uniqueness of the solution in the case of a polyhedral “torus”. Chapter 5 is dedicated to numerical simulations. First are introduced the terms of the dielectric tensor K and its derivatives, needed to mount the stiffness matrix of the system. The first simulations concern the case where the density of electrons and ions is constant. Then results are presented in the case where densities have a parabolic profile. It is also considered the case where the wave vector is a function of the distance at the center of the tokamak
Riad, Hassan. "Calcul du transfert radiatif dans des arcs et des plasmas thermiques : application à l'hydrogène et au méthane." Toulouse 3, 1996. http://www.theses.fr/1996TOU30178.
Militello, Fulvio. "Linear theory and saturation of tearing modes in plasmas." Aix-Marseille 1, 2006. http://www.theses.fr/2006AIX11027.
In this work, the linear theory and the saturation of the Tearing Mode in plasmas are investigated. This instability is associated to magnetic reconnection, and has been proved a valid model to explain several plasma processes, such as the solar flares, the behavior of Earth's magnetosphere and the physics of the experimental devices used in nuclear fusion research (Tokamak). Specific attention is devoted to the influence of the asymmetries of the equilibrium current density. It is shown that an asymmetric equilibrium can affect significantly both the linear dispersion relation of the mode and the overall saturation level. A rigorous mathematical procedure, which employs perturbative techniques, is developed to solve the nonlinear saturation problem. This procedure allows reliable predictions of the final width of the magnetic island associated with the instability. Three relevant physical regimes of plasma are investigated, depending on the model for the evolution of the resistivity, which may be affected by the growth of the mode. In the final section of the work, part of the analytical results obtained is employed in the understanding of the Tearing Mode in a physical framework relevant for fusion plasmas. In particular, the mathematical model is extended to include effects related to the so-called Neoclassical description of the Tokamak. The complexity of the nonlinear problem does not allow a straightforward analytical approach, and has to be handled with numerical tools. A systematic numerical investigation of the saturation of the Neoclassical Tearing Mode is presented, the results of which are interpreted with a simplified theoretical model
Duez, Vincent. "Modélisation des Champs Magnétiques de Grandes Échelles dans les Intérieurs Stellaires : Application aux étoiles de type solaire et aux étoiles Ap." Palaiseau, Ecole polytechnique, 2009. http://pastel.paristech.org/5936/01/these.pdf.
Stellar astrophysics needs today new models of large-scale magnetic fields, which are observed through spectropolarimetry at the surface of Ap/Bp stars, and thought to be an explanation for the uniform rotation of the solar radiation zone, deduced from helioseismic inversions. During my PhD, I focused on describing the possible magnetic equilibria in stellar interiors. The found configurations are mixed poloidal-toroidal, and minimize the energy for a given helicity, in analogy with Taylor states encountered in spheromaks. Taking into account the self-gravity leads us to the “non force-free” equilibria family, that will thus influence the stellar structure. I derived all the physical quantities associated with the magnetic field ; then I evaluated the perturbations they induce on gravity, thermodynamic quantities as well as energetic ones, for a solar model and an Ap star. 3D MHD simulations allowed me to show that these equilibria form a first stable states family, the generalization of such states remaining an open question. It has been shown that a large-scale magnetic field confined in the solar radiation zone can induce an oblateness comparable to a high core rotation law. I also studied the secular interaction between the magnetic field, the differential rotation and the meridional circulation in the aim of implementing their effects in a next generation stellar evolution code. The influence of the magnetism on convection has also been studied. Finally, hydrodynamic processes responsible for the mixing have been compared with diffusion and a change of convection’s efficiency in the case of a CoRoT star target
Crouseilles, Nicolas. "Contributions à la simulation numérique des modèles de Vlasov en physique des plasmas." Habilitation à diriger des recherches, Université de Strasbourg, 2011. http://tel.archives-ouvertes.fr/tel-00529809.
Nishimura, Seiya. "Study on multi-scale nonlinear dynamics of magnetic islands in tokamak plasmas." Aix-Marseille 1, 2009. http://www.theses.fr/2009AIX11060.
This thesis is devoted to the modelling and simulation of the nonlinear dynamics of a magnetic island in presence of a pressure gradient in a tokamak plasma. This mode called “drift tearing” is in fact a tearing mode coupled to an electronic drift wave. Tearing instabilities play an important role in the magneto-hydrodynamic stability of thermonuclear fusion plasmas. It is admitted that these instabilities will determine the pressure limit in future plasma tokamak reactors like ITER. There are still many open questions related to the conditions of appearance as well as the nonlinear dynamics of these modes. An important issue is the island rotation which develops during a tearing instability. Indeed, the rotation speed as well as its sign have an important impact on the nonlinear evolution of the magnetic island. In this thesis the physical mechanisms underlying this rotation are explored. An important result is that the rotation direction of the island depends on the viscosity and the resistivity parameters. To understand this phenomenon, a model is developed and validated by numerical simulations. A practical result is derived from this model: the rotation frequency of the magnetic island increases with the magnetic Prandtl number
Tsikata, Sedina. "Small-scale electron density fluctuations in the hall thruster, investigated by collective light scattering." Palaiseau, Ecole polytechnique, 2009. http://tel.archives-ouvertes.fr/docs/00/48/40/27/PDF/thesis.pdf.
Anomalous electron transport across magnetic field lines in the Hall thruster plasma is believed to be due in part to plasma oscillations. Oscillations of frequencies on the order of a few megahertz and of wavelengths on the order of a millimeter have been shown to be likely to lead to transport. Measurements of fluctuations at these length scales is, however, beyond the reach of conventional thruster diagnostics such as probes. This work describes the first application of a specially-designed collective light scattering diagnostic (PRAXIS) to the measurement of electron density fluctuations and the subsequent identification of unstable modes in the thruster plasma. Two main high frequency modes are identified, propagating azimuthally and axially, of millimetric length scales and megahertz frequencies. The propagation directions and angular openings of the modes are determined. The azimuthallypropagating mode, believed to be responsible for transport, is shown to have wave vector components antiparallel to the magnetic field and parallel to the electric field, and to propagate within an extremely limited region. The axially-propagating mode is shown to have features closely related to the ion beam velocity and divergence. The electron density fluctuation level is calculated and is associated with a high electric field amplitude. The experiments, confirming a number of predictions arising from linear kinetic theory, also provide much additional information permitting the improvement and development of models for both modes
Labit, Benoît. "Transport de chaleur électronique dans un tokamak par simulation numérique directe d'une turbulence de petite échelle." Aix-Marseille 1, 2002. http://www.theses.fr/2002AIX11052.
Bian, Nicolas. "Turbulence convective et transport intermittent dans un plasma magnétisé." Aix-Marseille 1, 2002. http://www.theses.fr/2002AIX11012.
Lemou, Mohammed. "Etude mathématique et résolution numérique de l'équation de Fokker-Planck-Landau en physique des plasmas." Toulouse 3, 1996. http://www.theses.fr/1996TOU30270.
Tamain, Patrick. "Etude des flux de matière dans le plasma de bord des tokamaks : alimentation, transport et turbulence." Aix-Marseille 1, 2007. http://www.theses.fr/2007AIX11060.
Particle transport in the edge of tokamaks plays a decisive role both in the center on plasma performances, since it governs the building of density profiles from external particle fuelling, and in the edge on the lifetime of plasma facing components, since it determines particle and energy fluxes reaching the wall. However, this subject has been little explored due to the complexity of modelling the interaction, in the same volume, of the plasma with strong particle, momentum and energy sources and sinks. In the perspective of ITER, the capability of gas puffing systems to reach required density levels without degrading the confinement, as well as the properties of density profiles and flows near the pedestal and in the SOL, remain open questions. This thesis contributes to the effort aiming at giving a better understanding of the mechanisms governing particle fluxes in the edge plasma and their impact on these questions. In a first phase of our work, we present an original approach for the modelling of fuelling by gas puffing, focusing on the thermal impact of the injection on the plasma. On the basis of analytical and numerical models with a reduced number of dimensions, we demonstrate the existence of thermal bifurcations trigerred by the injection and their importance in the dynamics of the neutral penetration and of the plasma relaxation. In the case of Tore Supra, we show that the local cooling linked to a strong injection allows a deeper penetration of particles (r/a = 1. 1 to r/a = 0. 9), but can also lead to a thermal instability of the whole plasma below a given ratio heating power / particle source. The extrapolation of this study for ITER remains pessimistic on the penetration depth of neutrals. However, the sensitivity of the results of these simplified models to the interaction between the parallel and perpendicular directions show that the developpement of numerical tools modelling coherently particle transport in both directions is necessary to progress on these questions. This led to the design of a 3D code presented in the second part of this work. This new tool is a full-torus code, including curvature effects. It solves electrostatic fluid drift equations without scale separation hypothesis, which allows to address with the same tool issues linked to large scale transport as well as micro-turbulence. Two versions of the code have been developped and validated : one treats exclusively closed field lines ; the other, more demanding from the numerical point of view, includes both the Scrape Off Layer (SOL) and the external part of the confined plasma. In a last part, the code is used to address the issue of poloidal asymmetries of parallel flows in the SOL which are observed experimentally but whose origin is not fully clear yet. Simulations reproduce the order of magnitude of measured amplitudes and evidence two different mechanisms which are likely to play a role in this phenomenon, the first at large scales, the other linked to turbulence. The former leans on a coupling between large scale drifts and curvature effects in the SOL while the latter is linked to the ballooning of the radial turbulent flux on the low field side. Finally, the importance of the plasma parallel resistivity on the characteristics of the turbulent transport is analysed as well as the impact of a localized particle injection on the local properties of turbulence
Ben, Abdallah Naoufel. "Etude de modèles asymptotiques de transport de particules chargées : asymptotique de Child-Langmuir." Palaiseau, Ecole polytechnique, 1994. http://www.theses.fr/1994EPXX0003.
Décultot, Léa. "Étude et modélisation du procédé de refusion par plasma d’arc en creuset froid (PAMCHR) d’alliages de titane pour des applications aéronautiques." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0031.
The recycling of titanium scraps can be achieved using the Plasma Arc Melting Cold Hearth Refining (PAMCHR) process with the aim of producing aeronautical titanium alloy ingots. In this manuscript, the research work focuses on the refining stage of the process where the liquid is transported in a horizontal copper water-cooled crucible. This important step takes place downstream the melting of the charge and upstream the casting of liquid titanium into the ingot mold crucible. Plasma torches are used as heat source of PAMCHR process, which is conducted under an atmosphere of inert gas. A three-dimensional modeling of the thermo-hydrodynamic flow of the titanium alloy has been set up based on Ansys-Fluent CFD software. The purpose of this tool, named PAM3D, is to improve our understanding of the liquid titanium behavior within the refining crucible. A large number of user functions have been integrated into the model to describe, among other mechanisms, the thermal and momentum transferred from the plasma plume to the surface of the liquid bath. The analysis of these transfers is essential for modeling the process. They are obtained by a study coupling melting tests, carried out in a pilot PAMCHR furnace, and numerical modeling. Numerical results, obtained by this first version of PAM3D are compared to experimental measurements, and the agreement is satisfactory. However, the maximum value of the shear stress, due to the impact of the plasma plume on the bath surface, implemented in the model seems to be underestimated. Moreover, complementary simulations highlight the important role of hydrodynamic forces on the thermal behavior of the bath, and in particular of this shear stress
Leray, Gary. "PEGASES: Plasma Propulsion with Electronegative Gases." Phd thesis, Ecole Polytechnique X, 2009. http://pastel.archives-ouvertes.fr/pastel-00005935.
Jaoul, Cédric. "Étude par thermogravimétrie d'un procédé de nitrocarburation des aciers assisté par une post-décharge micro-ondes dans les mélanges N2-CH4 et Ar-N2-H2-C3H8 : diagnostic optique et modélisation de l'interaction gaz-surface." Vandoeuvre-les-Nancy, INPL, 2004. http://www.theses.fr/2004INPL113N.
N2-CH4 afterglow is first studied by optical emission spectroscopy. A method to measure densities of carbon and nitrogen atoms in the post-discharge is presented. The mass gains of pure iron sam pies during post-discharge nitrocarburising treatments are monitored by in situ thermogravimetry. The use of propane during sequenced treatments shows that the studied orocess allows the synthesis of various carbonitride configurations: monophased (E) or multi-phased compound layer. The modeling of volume kinetic processes in the gas phase suitably predict the order of magnitude of the densities for major species in the N2-CH4 post- discharge. Lastly, we propose original results obtained by coupling several models (chemical kinetics of the gas phase, surface kinetics and diffusion in the solid) in the case of post-discharge nitriding
Cismondi, Fabio. "Contrôle non destructif par thermographie infrarouge des composants face au plasma des machines de fusion contrôlée : modélisation et traitement statistique du signal associé." Toulon, 2007. http://www.theses.fr/2007TOUL0005.
In Plasma Facing Components (PFCs) the joint of the CFC armour material onto the metallic CuCrZr heat sink needs to be significant defects free. Detection of material flaws is a major issue of the PFCs acceptance protocol. A Non-Destructive Technique (NDT) based upon active infrared thennography allows testing PFCs on SATIR tests bed in Cadarache. Up to now defect detection was based on the comparison of the surface temperature evolution of the inspected component with that of a supposed "defect-free" one (used as a reference element). This work deals with improvement of thermal signal processing coming from SATIR. In particular the contributions of the thermal modelling and statistical signal processing converge in this work. As for thermal modelling, the identification of a sensitive parameter to defect presence allows improving the quantitative estimation of defect Otherwise Finite Element (FE) modelisation of SATIR allows calculating the so called deterministic numerical tile. Statistical approach via the Monte Carlo technique extends the numerical tile concept to the numerical population concept. As for signal processing, traditional statistical treatments allow a better localization of the bond defect processing thermosignal by itself, without utilising a reference signal. Moreover the problem of detection and classification of random signals can be solved by maximizing the signal-to-noise ratio. Two filters maximising the signal-to-noise ratio are optimized: the stochastic matched filter aims at detects detection and the constrained stochastic matched filter aims at defects classification. Performances are quantified and methods are compared via the ROC curves
Lesur, Maxime. "The Berk-Breizman Model as a Paradigm for Energetic Particle-driven Alfvén Eigenmodes." Phd thesis, Ecole Polytechnique X, 2010. http://tel.archives-ouvertes.fr/tel-00563110.
Davoine, Xavier. "Accélération électronique par sillage laser et sources de rayonnements associées." Versailles-St Quentin en Yvelines, 2009. http://www.theses.fr/2009VERS0057.
With laser wakefield acceleration, compact electron accelerators can be obtained in comparison with conventional accelerators. In addition, the resulting electron beams display original properties. This method deals with the use of an ultra-short and ultra-intense laser pulse. While propagating in low density plasma, the laser pulse creates in its wake a plasma wave with electrical field amplitude much larger than in conventional accelerator (by several orders of magnitude). This wakefield can strongly accelerate electron beams in few millimetres or centimetres up to energy from tens of MeV to several GeV. The accelerator size is then considerably reduced. The electron beams generated with wakefield acceleration can be used to produce X and Gamma-rays by diverse methods, for instance by using conversion targets or wigglers. The work achieved in this thesis is essentially numerical. The laser-plasma interaction is modelled with the code Calder. The simulations have allowed to better understand the physics involved, in particular when the electrons are injected thanks to the colliding pulse scheme. This scheme allows to improve the beam quality and to control its properties. Finally a code based on a different model and algorithms has been studied. This new code allows to considerably reduce the simulation length
Vergne, Pierre-Jean. "Simulation numérique d'un arc de disjoncteur à hexafluorure de soufre en présence d'un écoulement turbulent en régime stationnaire." Toulouse 3, 1995. http://www.theses.fr/1995TOU30056.
Isoardi, Livia. "Modelisation du transport dans le plasma de bord d'un tokamak." Aix-Marseille 3, 2010. http://www.theses.fr/2010AIX30066.
Deluzet, Fabrice. "Modélisation mathématiques et simulation numérique de commutateurs d'ouverture à plasma." Toulouse, INSA, 2002. http://www.theses.fr/2002ISAT0002.
This thesis deals with plasma opening switches modeling and simulation. Space charge separation effects are determinant in explaining the operating of such devices, and to deal with these phenomena, we consider a bi-fluid model for the plasma. The Maxwell's equations describe the change in electromagnetic field. Hydrodynamic equations are regarded to represent the ionic fluid. An asymptotic model, in which particles inertia is neglected, is considered for electrons. This model is referred to as the energy-transport model. In this thesis, we first give an extension of the energy-transport model in the context of relativistic electrons. We then study the classical limit of this model with the help of a modal analysis. We finally develop numerical methods to discretize the bi-fluid model coupled with the Maxwell's system. Fluid equations are discretized thanks to Particle-In-Cell and Fluid-Implicit-Particle methods in order to derive an implicit scheme for the electronic energy equation. The Maxwell's equations are finite differenced an a cartesian mesh. This work is ended by a set of simulations aimed at presenting different phases of the plasma opening switches operating. The stability of the schemes is demonstrated and we emphasize the importance of boundary conditions to give an accurate representation of determinant phenomena
Regnier, Christophe. "Dépot chimique en phase vapeur d'oxydes (SiO2, Al2O3) sur des substrats métalliques dans une post-décharge micro-onde : caractérisation des films et modélisation du plasma d'oxygène." Limoges, 1995. http://www.theses.fr/1995LIMO0042.
Métral, Jérôme. "Modélisation et simulation numérique de l'écoulement d'un plasma atmosphérique pour l'étude de l'activité électrique des plasmas sur avion." Châtenay-Malabry, Ecole centrale de Paris, 2002. http://www.theses.fr/2002ECAP0868.
A ionized gas (or plasma) has the ability of absorbing or reflecting electromagnetic (radar) waves if its ionization rate is high enough. This is particularly interesting for aeronautics. This study aims at predicting the electric and energetic characteristics of a weakly ionized air plasma in an atmospheric pressure flow. The plasma is described by a two-temperature model, coming from the non-equilibrium description of plasmas. Plasma flow is then described by a two-temperature hydrodynamic system coupled with a collisional model (energy exchanges rates) and a kinetic model (chemical reactions). An algorithm was built to simulate plasma flow in axisymetric geometry. The algorithm is a 2D Lagrange + Projection scheme. The projection step was adapted to multi-components advection, using a second order, non oscillating, and bidimensionnal scheme. This algorithm allows the simulation of experiments concerning atmospheric pressure plasma and then the validation of the model parameters. In a second part, we study the Perfectly Matched Layer (PML) which is a boundary condition to simulate wave propagation in open domains. This method is particularly efficient for electromagnetic problems, and we want to enlarge this approach to aeroacoutics problems (linearized Euler equations). We propose two solutions: a practical approach to avoid numerical oscillations of the solution and a more general approach which consists in a new absorbing layer formulation which leads to well-posed problems
Hattori, Takashi. "Décomposition de domaine pour la simulation Full-Wave dans un plasma froid." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0380/document.
In order to generate current in tokamak, we look at plasma heating by electromagnetic waves at the lower hybrid (LH) frequency. For this type of description, one use a ray tracing code but we consider a full-wave one, where dielectric properties are local.Our aim is to develop a finite element numerical method for the full-wave modeling and to apply a domain decomposition method. In this thesis, we have developped a finite element method in a cross section of the tokamak for Maxwell equations solving the time harmonic electric field and a nonoverlapping domain decom- position method for the mixed augmented variational formulation by taking continuity accross the interfaces as constraints
Salanne, Jean-Philippe. "Contrôle du point de fonctionnement des décharges électriques par l'intermédiaire de leur alimentation." Toulouse, INPT, 2005. http://ethesis.inp-toulouse.fr/archive/00000167/.
The aims of this study is to control the operating point of electrical discharges. These points, resulting from the coupling between the power supply and its load, may be unstable because of the dynamic behaviour of the discharge or any change of its length. To optimize the design and the electronic control of the power supply, the couplings between the later and the discharge are prospected. Numerical and analytical models of the system are presented. These models can simulate the couplings between the power supply and a discharge and are used to achieve the design of the power supply and its control. This approach is completed by experimental investigations considering discharge between 2 points, glidarc and DBD
Bonnement, Audrey. "Modélisation numérique par approximation fluide du plasma de bord des tokamaks (projet ITER)." Nice, 2012. http://www.theses.fr/2012NICE4088.
Magnetic confinement fusion allows to favour fusion reactions and energy production with toric devices, called tokamaks, using an electro-magnetic field in order to confine the plasma. To study the edge plasma of tokamak, we use a fluid model, obtained from the Vlasov-Maxwell kinetic model and the Braginskii closure. A finite volume/element method is chosen to approach the model. The system is similar to the Euler or anisotropic Navier-Stokes systems, with additional terms to model the plasma confinement. We propose some methods to approach these terms and to model Bohm boundary conditions, characteristic of tokamak. Moreover, a finite volume method in cylindrical coordinates is proposed in order to preserve the conservative form of the equations. Thus, we consider as elementary volume, the cell which is given by rotation around the tokamak axis of the 2D cell. Several numerical results are given, e. G. For an anisotropic diffusion problem with radiation and also for simulations of pellet injections (matter ice cubes) to refuel the tokamak
Martin, Marie. "Modélisations fluides pour les plasmas de fusion : approximation par éléments finis C1 de Bell." Phd thesis, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00845922.
Van, Box Som Lucile. "Des naines blanches magnétiques accrétantes aux plasmas laser : simulations, similitudes et expériences." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS555.
Magnetic white dwarfs are part of some binary systems which accrete matter from their companion star as an accretion column. The accretion flow confined by the magnetic field lines falls at a supersonic velocity onto the magnetic poles of the white dwarf. At the impact, an accretion shock is generated and the post-shock region is structured as a result of the effects of complex radiative processes. In this work, we present observational data, astrophysical numerical data, theoretical studies and finally experimental data obtained on different laser facilities as well as their associated numerical simulations. First, theoretical and numerical studies at the astrophysical scale describe the structure and the dynamics of the accretion column. In particular, we have studied the origin of rapid oscillations observed in the optical light curves of some objects. Then, we have completed these studies with an experimental approach to build laboratory millimetre-scaled models of the radiation hydrodynamic processes occurred in the accretion column through powerful lasers. Experimental results obtained on the GEKKO XII laser facility and their interpretations are presented. Finally, we have optimized a new experimental design to achieve a similar regime on megajoule facilities in indirect drive. The data obtained from such experiments will provide new insights to improve astrophysical modelling
Judée, Florian. "Liquides activés par jet de plasma froid pour le traitement sélectif du cancer colorectal : synthèse, caractérisation et essais thérapeutiques sur modèles cellulaires 3D in vitro et in vivo." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30344/document.
Plasma devices at atmospheric pressure (AP) generate many physical active species (photons, charged particles, electric field, etc.) and chemical (free radicals, reactive oxygen species, reactive nitrogen species, etc...). This species are well known for their direct or indirect biological effects thus biomedical treatment by low temperature plasma jets at AP is currently a hot research topic. The upsurge of radioresistance and chemoresistance of microorganisms and cancer cells requires the development of new biomedical treatment. In this general context, the present work is a step towards the understanding of the effect induced by low temperature plasma jets at atmospheric pressure on colorectal cancer (second leading cause of death by cancer in France). This thesis focuses on the implementation of an in vitro biological model (multicellular tumor spheroid of colorectal cancer HCT116) in 3 dimensions which allows to take into account key parameters in tumor proliferation. This model is also well suited for the prediction of in vivo results in the aim of a subsequent clinical study. Further research about kinetic reactions of active species has been studied from the plasma device up to intracellular interactions through physical, biological and chemical analyses. Indirect treatment of tumors was carried out through helium plasma jet activated liquids. This solution was chosen for its relevance for endoscopic treatment of colorectal cancer. Interaction between plasma activated liquid and multicellular tumor spheroids has shown two distinct pathways. The first one is the genotoxicity of activated medium induced by the occurrence of hydrogen peroxide which induced DNA damages once penetrated in intracellular medium and leading to cell death by apoptosis. A direct interaction between free radicals generated in liquid medium and the latter components (amino acids, glucose, etc.) associated with the occurrence of nitrites and nitrates induces a long-term antiproliferative effect of plasma activated liquid. Chemical pathways of the formation of these active species were identified by using different analysis techniques such as electron paramagnetic resonance and optical emission spectroscopy. Therapeutic analysis have also demonstrated that plasma activated liquid damage preferentially colon cancer cells rather than healthy cells making it a particularly promising selective treatment method. The design and the characterization of a second plasma jet using argon as a carrier gas was carried out with the aim to improve the antiproliferative effect of plasmas on tumors while taking into account the requirement for the use of such device for colorectal cancer treatment
Mage, Lucile. "Caractérisation d'un réacteur plasma de type résonance cyclotronique électronique à antenne longue : évaluation du réacteur pour un processus de dépôt." Toulouse 3, 1997. http://www.theses.fr/1997TOU30174.
Crispel, Pierre. "Modélisation mathématique et simulation de la transition d'une décharge électrostatique primaire vers un arc électrique secondaire entretenu par la puissance photovoltaïque d'un générateur solaire de satellite." Toulouse, ENSAE, 2005. http://www.theses.fr/2005ESAE0021.
Fontaine, Adrien. "Relations de dispersion dans les plasmas magnétisés." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S029/document.
This thesis describes how electromagnetic waves propagate in magnetized plasmas, when the frequencies are in a range around the electron cyclotron frequency. It focuses on the mathematical analysis of the characteristic varieties which are associated with relativistic Vlasov-Maxwell systems involving fast parameters. The first part is concerned with cold plasmas issued from planetary magnetospheres. We explain how to obtain the dispersion relations in the case where the magnetic field is given by a dipole model. This leads to the detailed study of some algebraic varieties from the cotangent space: the so-called ordinary and extraordinary cones and spheres. The geometrical description of these cones and spheres gives access to a complete classification of the electromagnetic waves which can propagate. Various applications are proposed, concerning the eikonal equation and the absence of purely parallel propagation, or concerning the structure of whistler waves. The second part focuses on the modelling of hot plasmas, typically like those involved in tokamaks. We prove in a realistic context that the propagation of electromagnetic waves is governed by some dielectric tensor. This tensor is obtain via some careful analysis of the kinetic resonances, which are issued from the interactions between the particles (Vlasov) and the waves (Maxwell). It can be expressed as an infinite sum of singular integrals, involving the Hilbert transform. The mathematical meaning of the formula defining this tensor is rigorously justified
Sladkov, Andrey. "Numerical modeling of magnetic reconnection in laser-induced high energy density plasmas." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS376.
This thesis is a numerical study of the magnetic reconnection in collisionless plasmas using a kinetic code. We can study the magnetic reconnection process during experiments for which the plasma is created by interaction of a power laser on a solid target. During this thesis, we included in the HECKLE code the elements allowing to make these simulations more realistic for the laser conditions: the effects of the electron six-component pressure tensor as well as the super-Alfvénic expansion of the plasma. We have thus highlighted the role of the pressure tensor to reduce the efficiency of the reconnection, as well as the plasma temperature effects making it more impulsive
Dejarnac, Renaud. "Etude du plasma de bord du tokamak Tore Supra en vue de l'optimisation du pompage des particules et de l'injection supersonique de matière." Aix-Marseille 1, 2002. http://www.theses.fr/2002AIX11055.
Chable, Stéphane. "Modélisation numérique d'un propulseur à plasma stationnaire." Toulouse, ENSAE, 2003. http://www.theses.fr/2003ESAE0007.
Gélix, Franck. "Modélisation des phénomènes de transport au sein d'un four à plasma." Bordeaux 1, 1999. http://www.theses.fr/1999BOR10665.
Bianchetti, Morales Rennan. "Density profile reconstruction methods for extraordinary mode reflectometry." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0031/document.
The goal of this PhD is to improve the data analysis techniques of frequency swept reflectometry for determination of the density profile of fusion plasmas. There has been significant improvements in the last two decades on the hardware design and signal extraction techniques, but the data analysis is lagging behind and require further improvements to meet the required standards for continuous operation in future reactors. The improvements obtained in this thesis on the reconstruction of density profiles provide a better accuracy in a shorter time, even in the presence of a density hole, also enabling sufficiently precise measurements of the properties of turbulence used to validate numerical models, and allowing real-time monitoring of the shape and position of the plasma
Nelson, David. "Modélisation des données de base ioniques appliquées à l'étude électrique des réacteurs plasmas de dépollution des gaz d'échappement." Toulouse 3, 2002. http://www.theses.fr/2002TOU30097.
These research works are devoted to the determination of ion swarm basic data in gases and atmospheric gas mixtures and to the numerical simulation of charged particles transport in cold non thermal plasmas. With regard to the ion swarm data, it concerns the determination of the interaction potential, the collision cross section sets of both elastic and inelastic processes and the transport coefficients (drift velocity, reduced mobility, diffusion and reaction coefficients) specific for each ion-molecule system in flue gases including N2, O2, CO2 and H2O molecules. .
Leghtas, Lahoucine. "Modélisation en ondes millimétriques du TEC froid : application aux modulateurs microondes." Lille 1, 2003. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2003/50376-2003-243.pdf.
Parisot, Martin. "Modélisation intermédiaire entre équations cinétiques et limites hydrodynamiques : dérivation, analyse et simulations." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10052/document.
This work is devoted to the study of a problem resulting from plasma physics: heat transfer of electrons in a plasma close to Maxwellian equilibrium. Firstly, the asymptotic regime of Spitzer-Harm is studied. A model proposed by Schurtz and Nicolai is analyzed and located in the context of hydrodynamic limits outside of the strictly asymptotic. The link to non-local models of Luciani and Mora is established, as well as the mathematical properties such as the principle of maximum and entropy dissipation. Then, a formal derivation from the Vlasov equations is proposed. A hierarchy of intermediate models between the kinetic equations and the hydrodynamic limit is described. In particular, a new system hydrodynamics, integro-differential by nature, is proposed. The system Schurtz and Nicolai appears as a simplification of the system resulting from the diversion. The existence and uniqueness of the solution of the nonstationary system are established in a simplified framework.The last part is devoted to the implementation of a specific numerical scheme for solving these models. We propose a finite volume approach can be effective on unstructured grids. The accuracy of this scheme to capture specific effects such as kinetic, which may not be reproduced by the asymptotic Spitzer-Harm model. The consistency of this pattern with that of the Spitzer-Harm equation is highlighted, paving the way for a strategy of coupling between the two models
Mercado, Cabrera Antonio. "Modélisation de la cinétique chimique d'un plasma en extinction dans un disjoncteur basse tension." Toulouse 3, 2003. http://www.theses.fr/2003TOU30007.